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Running a 110V motor on 220V

WorkshopJon's picture

All qualified electricians,

I've been doing major moving around of equipment in my shop and was trying to decide what to do with a JET 1236P (mfr '79) engine lathe I acquired many years back. It came with a 110V plug attached, has a 2HP dual voltage (on the tag) motor that draws 28/14amps depending on how its wired.

I've always had problems with the motor. It will only start if the motor has a zero (no belt) load, and will only power the lathe at lower loads. Any serious load will pop the 30amp breaker. It has a 20' dedicated 10gauge line.

Although it appears from the [Taiwanese] tag it can be wired for dual voltage, it appears to have been modified (there simply aren't enough wires coming out of it) for one voltage. So to cut to the chase.

Yesterday I hooked it up to a 220 source and it ran great. I only ran it for about 45 seconds, but even under a brief very heavy load did not overheat. So....

Anybody's thoughts would be welcome. What happens when a 110 motor is run on 220? What should I be looking for? A pic of the motor is attached for your amusement.


Edited 11/23/2003 1:00:56 PM ET by WorkshopJon

(post #110620, reply #1 of 13)

I would suggest taking to a motor shop and have then check exactly what the wires are.

From the sounds of it it "might have been" setup for 240 all along. But some idiot that that it was used whatever connectors that he had and used 120 volt plug.

Do you have a clamp on amp meter? Readings in each case would be helpfull.

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #110620, reply #2 of 13)

"Do you have a clamp on amp meter? Readings in each case would be helpful."


Unfortunately I don't, just the standard GB multimeter. I agree with you that I the motor is likely wired for 240V, but there really is no way to tell visually for sure. The lathe was very likely originally hard wired, and very easily could have had the wrong plug attached.

The wires that go to the forward reverse switch (power in) are green with a yellow stripe and yellow (no help there). The ones to the motor (from the switch), which are switched in pairs, are black, red, blue, and brown. (but who knows how the Taiwanese did things 20 plus years ago.)

That still leads me to suspect it's wired for 240V. all wires in/out of the motor are black and red, with 2 additional reds for the [remotely mounted] capacitors.

The gist of my question is, if you run a 110V motor on 240V (I actually have 126/252 as my house is the closes to the transformer on a long rural stretch) , what would be the warning signs before it toasted itself? What precautions should I take for a test?



Edited 11/23/2003 2:35:23 PM ET by WorkshopJon

(post #110620, reply #3 of 13)

Just a couple of thoughts. If you look at the picture you displayed, it looks like above the the wires is the motor identification plate. It might have some of the info your looking for, sometimes they display the wiring schematic. Also sounds like whoever had it before you may not have had 240V so they just had to run it on 120v and wired the plug accordingly.

 The other is use the motor manufacture to try to pull up info on the web, sometime it's amazing what we can pull up.

(post #110620, reply #4 of 13)


Yes, there is a tag with a wiring schematic. The problem is that it shows 6 wires coming out of the motor (in addition to the 2 from the caps) and there are only 4 (plus the 2 from the caps).

 The area on the motor where one would normally find the box that would have housed the various wires and connections (to swap voltages) was clearly removed at the factory and replaced with a rubber cover with holes in it that the wires pass through, as it interfered with the design of the lathe.

More background: This was acquired from a friend (now deceased) who went in and bought an entire shop at a firesale price. Went into the shop and basically ripped everything out. Just cut hardwired stuff etc. The shop had everything from 110V to 440V three phase powered equipment.

I just want to know what is the easiest cheapest way to figure out what voltage it's wired for, given that the wires coming out of the motor are not labled and don't numerically match the tag.


(post #110620, reply #5 of 13)

I'm thinking that it sounds like it's a 3 phase motor and was wired wong to run on one leg of the 3 phase.

commerecial Electric is over my head so you need to go to bigger heads. I just was viewing some elec tric talk in another area so let me go back and I'll send you the link.


(post #110620, reply #8 of 13)

I looked at my message and saw I said Wong wireing, maybe it was made in china?


(post #110620, reply #10 of 13)

I have to disagree.......3 phase motors don't have start capicatators




(post #110620, reply #6 of 13)

This looks like a question for "JUNKHOUND!!!"

Thinking old Mighty Mouse or Superman cartoons here.......

Joe H

(post #110620, reply #11 of 13)

As others have said, almost certainly wired for 240 to start with.  If it is wired for 120 and you ran it without tripping the breaker on 240 V  it's quite an over designed motor - nearly all 120 wired motors when hooked across 240V will trip the breaker because the stator core will magnetically saturate, and draw very high peak currents when the sine wave goes over about 180-200 Vpeak.  Run it like it is on 240., just stay around for the first few hours to be sure you don't fill with smoke due to some unknown misconnection.

One item not mentioned is that nearly all dual voltage induction single phase motors these days and lots of lower priced old ones only have only a 240 V start winding, which is why a lot of 120 V wired motors have an anemic start, and tend to smoke if overloaded to a slower speed where the centrifugal switch or start relay kicks in often. The old sears radial arm saws on 120V were famous for smoking the start winding when trying to use RA for ripping.

A toy train transformer and simple Vac meter and resistor can be used to 'wring out' the windings, but the proceedure is to lengthy to explain tonight.

(post #110620, reply #12 of 13)

I'm real interested in reading about that, when you have the time, Art.

Live, Love, Forgive and Forget



It's a small world. Until you have to walk home...

(post #110620, reply #13 of 13)


(and 4LORN1, And Bill H. and...the others)

Thanks for the advice. Since I do not have a clamp over amp meter I figured the next best thing would be to drop the circuit breaker to to lowest I could find (a 7 amp) and run the motor for a while on that.

I started it under no load (belt not engaged) and gradually ramped up the load to a moderate level for about 20 minutes. I experienced no overheating and didn't blow the breaker. It did pop with the feed and high RPM engaged on a dead start(obviously a hard start), but think that it definitely was wired 240V all along.

Thanks again,



(post #110620, reply #7 of 13)

General Discussion -  Wiring q: safe and legal or

 Go here and ask a couple of Questions cause the real Electricians are here.


(post #110620, reply #9 of 13)

It ran weakly and tripped the breaker. Common to a 230v motor setup run on 115v. On 230v, 240v nominal, it runs well, has power, doesn't overheat or trip the breaker.

- You could:

Ring out the connections to check the wiring of the windings. If it is a dual voltage motor they will be in parallel for 115v and series for 230v.

Check the current draw and compare it to the name plate current.

Take it to a motor shop and have them tell you how it is.

- What I would do:

I would run and enjoy it. Check it for overheating every once in a while, particularly under load. You should be able to hold your hand on it without too much pain or any burns. When you stop working it unplug the unit just to be safe. At least for some amount of use I wouldn't leave it running or plugged in unattended. Of course keep flammables away from it. Always a good idea as any motor can lock up, overheat and throw sparks. Good housekeeping.